Network-based vaccination improves prospects for disease control in wild chimpanzees

Abstract

Many endangered wildlife populations are vulnerable to infectious diseases for which vaccines exist; yet, pragmatic considerations often preclude largescale vaccination efforts. These barriers could be reduced by focusing on individuals with the highest contact rates. However, the question then becomes whether targeted vaccination is sufficient to prevent large outbreaks. To evaluate the efficacy of targeted wildlife vaccinations, we simulate pathogen transmission and control on monthly association networks informed by behavioural data from a wild chimpanzee community (Kanyawara N ¼ 37, Kibale National Park, Uganda). Despite considerable variation across monthly networks, our simulations indicate that targeting the most connected individuals can prevent large outbreaks with up to 35% fewer vaccines than random vaccination. Transmission heterogeneities might be attributed to biological differences among individuals (e.g. sex, age, dominance and family size). Thus, we also evaluate the effectiveness of a trait-based vaccination strategy, as trait data are often easier to collect than interaction data. Our simulations indicate that a trait-based strategy can prevent large outbreaks with up to 18% fewer vaccines than random vaccination, demonstrating that individual traits can serve as effective estimates of connectivity. Overall, these results suggest that fine-scale behavioural data can help optimize pathogen control efforts for endangered wildlife.

Testosterone and reproductive effort in male primates

“…It is not clear from such studies, however, whether this relationship is driven by variation in immune function, or by other potential factors, such as exposure. In support of the latter hypothesis, social network analyses in one wild chimpanzee population showed that high-ranking males were more central, and thus more likely to be exposed to diverse pathogens (Rushmore et al 2013, 2014). Prall and Muehlenbein (2014) review major issues and methodological concerns in this area.…”

Heterogeneity in pathogen transmission: mechanisms and methodology

“…In chimpanzees ( Pan troglodytes ), models demonstrate that a greater proportion of the population becomes infected when epidemics originate in individuals with large numbers of direct contacts (Rushmore et al . ). Variation in contact degree and network position is reliant on the chimpanzee's complex social system emerging from kinship relationships, dominance hierarchies and ranging behaviour (Rushmore et al .…”

“…Epidemics that originated in individuals that displayed certain traits, such as having a large family or a home range located centrally in the community, were associated with larger outbreaks (Rushmore et al . ). Outbreak size was predictable from these trait‐based approaches because traits approximated network position (Rushmore et al .…”

Infectious disease and group size: more than just a numbers game

“…If so, these social barriers would offset the increased potential for an infectious agent to spread in larger groups, and thus reduce the overall association between group size and infectious disease risk (although it need not eliminate the association completely). Several studies have investigated aspects of this 'social bottleneck hypothesis' [30][31][32]. In a study that directly investigated network structure in non-human primates, Griffin & Nunn [29] found a positive association between group size and social network subdivision (community modularity), and negative associations between modularity and parasite richness (including micro-and macroparasites).…”